Objectif : Evaluer le niveau de contamination des eaux souterraines de Zouan-Hounien en élément traces métalliques (ETM). Méthodologie et résultats : Un total de soixante-douze (72) échantillons d’eaux souterraines ont été prélevés en raison de quarante-six échantillons d’eaux de puits (23 puits) et vingt-six échantillons d’eaux de forages (13 forages). Dans ces échantillons, des ETM tels que : Hg, Pb, Cd, As et Fe ont été dosés par spectrométrie d’absorption atomique. Les concentrations moyennes respectives de Fe, Pb, Hg, As et Cd sont de 2233,48 > 3,10 > 1,67 > 1,18 > 0,08 µg.L-1 dans les puits et de 2427,94 > 4,08 > , 2,36 > 1,76 > 0,08 µg.L-1 dans les forages. La valeur moyenne du degré de contamination (Dc) dans les puits et les forages est supérieure à 3, indiquant ainsi une forte contamination des eaux souterraines. Avec des valeurs moyennes de l’indice de pollution par les ETM (HPI) inférieures à la valeur seuil de 100, ces eaux restent faiblement polluées dans l’ensemble. Pourtant, deux puits et deux forages ont enregistré une forte pollution des eaux, avec des valeurs supérieures à 100. Conclusion : L’indice de pollution des eaux souterraines par les ETM appliqué aux eaux souterraines révèle que les eaux de puits et de forages sont de bonne qualité, à l’exception de deux puits et deux forages. Le mercure reste le principal élément qui contribue à la toxicité des eaux. Sa présence dans les eaux est due à l’effet des activités d’orpaillage ancien et actuel dans la zone. Une sensibilisation sur les impacts de l’orpaillage sur les ressources en eau est à mener au sein des orpailleurs afin de réduire l’utilisation du mercure. Une consommation prolongée de ces eaux peut entrainer des problèmes graves de santé publique. Mots clés : indices de pollution, eaux souterraines, ETM, orpaillage, Zouan-Hounien Assessment of pollution indices by metallic trace elements of groundwater resources in the mining area of the department of Zouan-Hounien, Côte d´Ivoire. Objective : Assess the level of contamination of Zouan-Hounien groundwater with metallic trace elements (ETM). Methodology and results: A total of seventy-two (72) groundwater samples were taken that is forty-six well water samples (23 wells) and twenty-six borehole water samples (13 wells). In these samples, ETMs such as: Hg, Pb, Cd, As and Fe were determined by atomic absorption spectrometry. The respective average concentrations of Fe, Pb, Hg, As and Cd are 2233.48> 3.10> 1.67> 1.18> 0.08 µg.L-1 in the wells and 2427.94> 4 , 08>, 2.36> 1.76> 0.08 µg.L-1 in boreholes. The average value of the degree of contamination (Dc) in wells and boreholes is greater than 3, thus indicating a strong contamination of groundwater. With average values of the ETM pollution index (HPI) below the threshold value of 100, these waters remain slightly polluted. However, two wells and two boreholes recorded heavy water pollution, with values greater than 100. The correlation matrix carried out between the ETM and the HPI reveals that Hg is the main element, which contributes to the toxicity of the water. Conclusion: The ETM pollution indices for groundwater applied to waters revealed that well and borehole water are of good quality, with the exception of two wells and two boreholes. However, mercury remains the main element that contributes to the toxicity of water. Its presence in the waters is due to the effect of old and current gold panning activities in the area. Thus, raising awareness of the impacts of gold panning on water resources is to be carried out among gold panners in order to reduce the use of mercury. Prolonged consumption of these waters can lead to serious public health problems. Keywords: pollution indices, groundwater, ETM, gold panning, Zouan-Hounien

Contamination of lagoon sediments by trace metal elements constitutes a danger to water, living species and human health. The objective of this study is to evaluate the level of trace element contamination in the sediments of the Ouladine lagoon. Trace elements (Pb, Zn, Cu, Cd and Cr) were assayed in lagoon sediments using a VARIAN AA 20. The intensity of sediment contamination was estimated from the calculation of several indices, including the Contamination Factor (CF), the Modified Degree of Contamination (MDC) and the Sediment Pollution Index (SPI). Sediment toxicity was demonstrated by comparing the concentrations of the measured trace elements with the American Sediment Quality Guidelines (SQGs). The results show the order of abundance of the following sediment VEC levels: Cr (83.92 mg.kg-1)>Pb (62.03 mg.kg-1)>Zn (60.06 mg.kg-1)> Cu (13.76 mg.kg-1)> Cd (1.45 mg.kg-1). The Contamination Factor (CF) and the Modified Degree of Contamination (MDC) indicate low to considerable contamination. The SPI values show that the sediments of the Ouladine lagoon are slightly polluted except at station S7 where the sediments are healthy. Except for Zinc, the other measured TE (Trace elements) were found to be detrimental to the living organisms of the Ouladine lagoon at all the stations that were sampled.

In the department of Zouan-Hounien, gold mining is booming. This activity, marked by the excavation of rocks and the use of chemicals such as mercury, is likely to contaminate the region's groundwater resources and expose populations to serious diseases. This study aims to assess the health risks associated with the consumption of this water by the population. To this end, 72 groundwater samples were taken in eight (08) villages of the department at the rate of forty-six (46) well water samples and twenty-six (26) borehole water samples. A total of twenty-twenty-three wells and thirteen boreholes were sampled during two campaigns. An atomic absorption spectrometer (AAS) was used to determine the concentrations of metallic trace elements (MTEs), such as mercury (Hg), lead (Pb), cadmium (Cd), Arsenic (As), and iron (Fe) in the different samples. The daily exposure doses for oral ingestion (CDIing) and skin contact (Expderm) were calculated. The non-carcinogenic (HQ) and carcinogenic risks (CR) were estimated. The results show that the mean concentrations of Fe, Pb, Hg, As and Cd are respectively 2233.48 > 3.10 > 0.60 > 1.18 > 0.08 µg•L −1 in the wells and 2427.94 > 4.08 > 1.27 > 1.76 > 0.08 µg•L −1 in boreholes. Evaluating the risks to human health reveals that the mean values of hazard quotient (HQ) and cancer risk (CR) for all the elements in the wells and boreholes are lower than 1 and 10 −4 respectively in children and adults for oral and dermal exposure. However, at the oral exposure level, 9 wells and 6 boreholes recorded HQ and CR above the defined critical limits. These values indicate that the occurrence of non-cancerous